There are used many molded glass bodies manufactured by pressure-molding a glass material with molds, as optical elements for various optical devices such as a lens for a digital camera, an optical pickup lens for DVDs, a camera lens for a cell phone, and a coupling lens for an optical communication. A required level of molded glass bodies to be employed as such the optical elements is becoming much more higher, corresponding to the recent trend toward smaller-sized and higher-accurate optical products.
As a manufacturing method of such the molded glass body, there is known a method (for example, refer to Patent Literature 1) to previously prepare a glass preform having a predetermined mass and predetermined shape and to pressure-mold the glass preform by heating the glass preform with moldings (hereinafter, it is referred as a reheat pressing method).
On the other hand, as another method of manufacturing the molded glass body, there is known a method (for example, refer to Patent Literature 2) to drip a drop of molten glass on a mold whose temperature is kept to a predetermined temperature being lower than that of the drop of molten glass and to pressure-mold the drop with the molds before the drop of molten glass which has been chipped is cooled and solidified (hereinafter, it is referred as a liquid-drop molding method).